The invention relates to a cutting tool for discshaped metal sheets.
By metal sheets, partly-machined flat rolled steel sheets are intended, having the dimension much smaller than the other two; in other words, metal sheets which are thin but thick enough to be further reduced in width by subdivision into further sheets.
The metal sheets specifically referred to are those having disc shape.
The prior art embraces tools which are substantially disc-shaped, which narrow down in the proximity of the external perimeter which perimeter functions as a knife and wedge to penetrate into the width of the sheet in order to obtain a partial separation into two sheets, thus producing a "Y"-shaped conformation in which the "arms" of the letter "Y" represent the two separated sheets, while the "leg" represents the uncut sheet.
Such tools are particularly applied in the making of pulleys, since they can perform on a single metal sheet, thus avoiding the necessity of welding two distinct parts which together constitute the pulley.
With regard to the making of pulleys, the prior art embraces both methods where a welding of two distinct parts is envisaged, and methods where the pulleys are realised from a single block of diskshaped metal by using tools as described above.
Such tools however have several drawbacks. Their maximum penetration depth is limited and rather modes. It has been found that the tool advancement towards depths greater than the thickness of the metal sheet happens with intolerable deviations from the original advancement plan, provoking deformations, undulations and sometimes even complete breaking of the metal sheet.